https://www.fau.edu/newsdesk/articles/ancient-dna-south-america
The Americas were the last continent to be inhabited by humans. An
increasing body of archaeological and genomic evidence has hinted to
a complex settlement process. This is especially true for South America,
where unexpected ancestral signals have raised perplexing scenarios
for the early migrations into different regions of the continent.
Many unanswered questions still persist, such as whether the first
humans migrated south along the Pacific coast or by some other route.
While there is archaeological evidence for a north-to-south migration
during the initial peopling of the Americas by ancient Indigenous
peoples, where these ancient humans went after they arrived has
remained elusive.
Using DNA from two ancient human individuals unearthed in two
different archaeological sites in northeast Brazil – Pedra do Tubarão
and Alcobaça – and powerful algorithms and genomic analyses, Florida Atlantic University researchers in collaboration with Emory University
have unraveled the deep demographic history of South America at the
regional level with some unexpected and surprising results.
Not only do researchers provide new genetic evidence supporting
existing archaeological data of the north-to-south migration toward
South America, they also have discovered migrations in the opposite
direction along the Atlantic coast – for the first time. The work
provides the most complete genetic evidence to date for complex
ancient Central and South American migration routes.
Among the key findings, researchers also have discovered evidence of Neanderthal ancestry within the genomes of ancient individuals from
South America.
Results of the study, published in the journal Proceedings of the Royal
Society B. (Biological Sciences), suggest that human movements closer
to the Atlantic coast eventually linked ancient Uruguay and Panama in
a south-to-north migration route – 5,277 kilometers (3,270 miles) apart.
This novel migration pattern is estimated to have occurred approximately
1,000 years ago based on the ages of the ancient individuals.
Findings show a distinct relationship among ancient genomes from
northeast Brazil, Lagoa Santa (southeast Brazil), Uruguay and Panama.
This new model reveals that the settlement of the Atlantic coast occurred
only after the peopling of most of the Pacific coast and Andes.
...
To further add to the existing complexity, researchers also detected
greater Denisovan than Neanderthal ancestry in ancient Uruguay and Panama individuals. Denisovans are a group of extinct humans first identified
from DNA sequences from the tip of finger bone discovered around 2008.
“It’s phenomenal that Denisovan ancestry made it all the way to South America,” says John Lindo, Ph.D., a co-corresponding author of the article who specializes in ancient DNA analysis and is an assistant professor in the Department of Anthropology at Emory University. “The admixture must
have occurred a long time before, perhaps 40,000 years ago. The fact that
the Denisovan lineage persisted and its genetic signal made it into an
ancient individual from Uruguay that is only 1,500 years old suggests that
it was a large admixture event between a population of humans and Denisovans.”
...
https://royalsocietypublishing.org/doi/epdf/10.1098/rspb.2022.1078
Genomic evidence for ancient human migration routes along
South America's Atlantic coast
Abstract
An increasing body of archaeological and genomic evidence has
hinted at a complex settlement process of the Americas by humans.
This is especially true for South America, where unexpected ancestral
signals have raised perplexing scenarios for the early migrations into different regions of the continent. Here, we present ancient human
genomes from the archaeologically rich Northeast Brazil and compare
them to ancient and present-day genomic data. We find a distinct
relationship between ancient genomes from Northeast Brazil,
Lagoa Santa, Uruguay and Panama, representing evidence for ancient
migration routes along South America's Atlantic coast. To further add
to the existing complexity, we also detect greater Denisovan than
Neanderthal ancestry in ancient Uruguay and Panama individuals.
Moreover, we find a strong Australasian signal in an ancient genome
from Panama. This work sheds light on the deep demographic history
of eastern South America and presents a starting point for future
fine-scale investigations on the regional level.
"Here, we report newly sequenced genomes from two
ancient human individuals (Brazil-2 and Brazil-12) unearthed
in two different archaeological sites in Northeast Brazil..."
"Consistent with previously reported data, our results
suggest that at least one population split probably occurred
not long after the first SNA groups reached the southern portion
of the Americas (figures 1b and 4a,b). Based on the
qpGraph results, we can hypothesize that this split took
place around the Andes, later giving rise to ancient Southern
Cone populations and the first groups that settled the
Atlantic coast (figures 4a,b and 5). In light of Sumidouro5’s
associated chronology—the oldest South American analysed
here—it is possible to affirm that the split occurred at least
10 000 years ago. Because Sumidouro5 is associated with
the ancestors of both Brazil-2 and CH19B (figures 1b and
4), we can further conjecture that new migrations may have
then emerged along the Atlantic coast, with Lagoa Santa as
the putative geographical source of waves that headed in
north-to-south and south-to-north directions—with the
latter seemingly reaching Panama (figures 1b, 4a,b and 5).
We conclude this hypothesis proposing that human movements
closer to the Atlantic coast eventually linked
Uruguay and Panama in a south-to-north migration route
(figures 4c,d and 5). The migrations along the Atlantic coast
apparently left no trace in the populations closer to the Pacific,
as we could not find back-migration events in that
direction (figure 4c,d)."
"In this study, the genomic data of 13 ancient human individuals
from the Americaswere used as a comparative dataset for the analyses
of the Northeast Brazil samples. These 13 ancient samples
from the Americas were selected based on two criteria: mean
sequence depth and geographical sampling location. Our goal
was to gather comparative data from the most diverse regions
within the Americas while still striving for the highest-quality genomes available for a given geographical region. Thus, we chose
USR1 from Alaska as the representative of ancient Beringia;
Anzick-1 from Montana, and three samples (Spirit Cave, Lovelock
2 and Lovelock 3) from the Spirit and Lovelock caves in Nevada to
represent the Southern North American (SNA) branch;
PAPV173 from Panama for Central America; IL2, IL3 and IL7
for the Andes in Peru; A460 from the western Southern
Cone (Chile); CH19B and CH13 from the eastern Southern
Cone (Uruguay) and Sumidouro5 from the Lagoa Santa
archaeological area in Brazil, the geographically closest
sample to Northeast Brazil (figure 1a; electronic supplementary
material, data S1). The ancient comparative dataset was complemented
with two archaic human samples, Altai Neanderthal
and Denisova, both from the Denisova Cave in Russia.
These two archaic samples represent the highest-quality genomes
available, in terms of sequence read depth, for Neanderthals and
Denisovans, respectively, and were used to assay archaic ancestry
in the ancient samples. Finally,we also employed a reference panel
of 253 present-day individuals from the SGDP. This presentday
dataset was specifically chosen because it is composed of
worldwide Indigenous populations assumed to span much of
the human genomic variation ."
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